This invention relates to the field of orthodontic appliances. More specifically, this invention relates to biasing apparatus for orthodontic appliances of the type used to effect palate widening.
As will be recognized by those skilled in these arts, it is often desirable or necessary for an orthodontist to cause a widening of the upper arch of patient's mouth. Such widening may be desirable in order to develop sufficient room for teeth to fit into place, to align upper teeth with lower teeth or to correct for high palate and narrow arch, e.g. to improve breathing. For whatever the reason, such palate widening has been achieved for the most part by cementing an appliance between the teeth of a patient and gradually expanding the appliance to generate an outwardly directed bias.
Typical examples of known biasing devices are disclosed in U.S. Pat. Nos. 360,695; 3,284,902 and 3,832,778. Such known appliances, as well as others, suffer from various disadvantages which render them undesirable from an orthodontic point of view as well as from the point of view of the patient.
From the orthodontist's point of view, known biasing devices are undesirable because it is required that a plurality of sizes be kept in stock. Thus, it is generally recognized in the field that orthodontic appliances having three basic sizes should be stocked in order to provide the range of expansion necessary for accommodating different sized mouths. Thus, a stock investment of significant proportion may be required either by the orthodontist or by the dental technician serving the orthodontist.
Further, in those cases wherein a large degree of expansion is required, it is a presently acceptable technique to commence pallate expansion with a small appliance and thereafter substitute a larger appliance in order to complete the amount of expansion required. This of course requires additional visits to the orthodontist`s office and subject the patient to undesirable additional discomfort.
A still further disadvantage from the orthodontists'point of view is that known apparatus are subject to reduction in bias by the patient. Specifically, with exposed operating threads there has occurred a backing-off of the threaded biasing members as a result of accidental manipulation by the patient. In known devices, once a desired expansion has been achieved, such backing off has been precluded by wiring the apparatus in place. Such wiring is not required by the present invention.
From the patient's point of view the known style orthodontic appliances create two particular problems, irritation and food retention.
As is clear from reference to the above-identified patents which are submitted to be typical of the prior art, there occurs in known orthodontic biasing appliances the exposure of the patient's tongue to the threaded surfaces of the operating device. Exposure of the tongue to such threaded surfaces invariably causes irritation, discomfort and, on occasion, laceration. Any such injury or discomfort is highly undesirable from the patient's point of view and a source of continuing difficulty for the orthodontist. In addition to the question of discomfort resulting from exposed screw threads attendant to the device, there is also the unhealthy and also discomforting tendency of known orthodontic biasing devices to retain food particles. Thus, the food may well become lodged in the operating mechanism of the known devices or it may become lodged partially in the operating mechanism and partially between the mechanism and the pallate of the user. It is evident that food so lodged is extremely difficult to remove and extremely undesirable from all standpoints.